1. Field of the Invention
This invention relates to power strip, also referred to as Relocatable Power Tap (RPT) having a Ground Leakage Monitor.
2. Description of the Related Art
Outlet strips or power strips, also referred to as Relocatable Power Tap (RPT) devices, are used to make access to electrical power more convenient. A typical RPT has several outlets each with line, neutral and ground connected via a conductor to a 3-wire plug for insertion into a wall outlet. The RPTs are rated at 250 volts or less and 20 amps or less. The grounding pin of the RPT plug serves to route potentially hazardous leakage current to ground.
The use of RPTs in hospitals and other patient care facilities has raised safety concerns primarily because of the increased risk of electric shock. For example, when several pieces of electrical equipment are plugged into an RPT, they are all connected to a single branch circuit via the attached conductor and plug inserted into a wall outlet. It is the grounding pin on the attached plug which is used to route potentially hazardous leakage current to ground. Since each connected electrical device does contribute an amount of leakage current to ground, the accumulated leakage current of several connected devices could create a risk of electric shock to a patient. Generally, the total leakage current is unknown, but in many instances, can exceed an upper permitted level which is typically 300 μA. Furthermore, as noted in the Underwriters Laboratories publication titled “The Code Authority” (spring 2004), if the grounding pin of the RPT attachment plug were damaged or removed, the accumulated leakage current of several connected electrical devices could create the risk of electrical shock. These concerns have caused RPTs to be considered unsuitable for use in a patient care environment.
Accordingly, there is a need for an improved RPT which can detect and monitor leakage current and, thus, can be used in hospitals and similar locations.